Methods for real-time image guided radiation therapy

Abstract

Disclosed herein are systems and methods for guiding the delivery of therapeutic radiation using incomplete or partial images acquired during a treatment session. A partial image does not have enough information to determine the location of a target region due to, for example, poor or low contrast and/or low SNR. The radiation fluence calculation methods described herein do not require knowledge or calculation of the target location, and yet may help to provide real-time image guided radiation therapy using arbitrarily low SNR images.

The invention claimed is: 
     
       1. A method for calculating a radiation dose for radiotherapy, the method comprising:
 acquiring a partial image x i  of a target region using at least one positron emission detector; 
 calculating a radiation fluence F i  to be delivered to the target region based on the partial image x i  and a radiation-firing matrix P; and 
 calculating a radiation dose using the calculated radiation fluence F i  and a computed tomography (CT) image. 
 
     
     
       2. The method of  claim 1 , further comprising comparing the calculated radiation dose with a planned radiation dose. 
     
     
       3. The method of  claim 1 , further comprising generating a graphical representation of the calculated radiation dose. 
     
     
       4. The method of  claim 1 , wherein calculating the radiation fluence comprises multiplying the radiation-firing matrix P and the partial image x i  (F i =P·x i ), wherein the radiation-firing matrix P is calculated based on a previously-acquired image X of the target region. 
     
     
       5. The method of  claim 1 , wherein the CT image is a CT image acquired during a diagnostic imaging session. 
     
     
       6. The method of  claim 2 , wherein calculating the radiation fluence F i  comprises multiplying the radiation-firing matrix P and the partial image x i  (F i =P·x i ), wherein the radiation-firing matrix P is calculated based on a previously-acquired image X of the target region, and wherein the method further comprises modifying the radiation-firing matrix P after comparing the calculated radiation dose with the planned radiation dose. 
     
     
       7. The method of  claim 1 , further comprising comparing the calculated radiation fluence with a planned radiation fluence. 
     
     
       8. The method of  claim 1 , wherein the partial image x i  comprises positron emission activity data. 
     
     
       9. The method of  claim 8 , wherein the positron emission activity data comprises one or more of PET data, lines-of-responses (LOR) data, and PET detector signals. 
     
     
       10. The method of  claim 9 , wherein the LOR data and/or PET detector signals comprise simulated LOR data and/or PET detector signals. 
     
     
       11. The method of  claim 1 , further comprising emitting the calculated radiation fluence to a phantom, and measuring radiation emitted to the phantom. 
     
     
       12. The method of  claim 11 , further comprising calculating a delivered fluence map based on the measured radiation and comparing the delivered fluence map with a planned fluence map. 
     
     
       13. The method of  claim 11 , further comprising calculating a delivered dose map based on the measured radiation, and comparing the delivered dose map with a planned dose map. 
     
     
       14. The method of  claim 13 , further comprising determining, based on the comparison between the delivered dose map and the planned dose map, whether a treatment plan meets specified quality criteria. 
     
     
       15. The method of  claim 14 , further comprising calculating a distance to agreement (DTA) value of fluence isodoses and an absolute dose difference between the delivered dose map and the planned dose map for multiple time points, determining whether a percentage of time points that are within a DTA value and within a specified absolute dose difference threshold is greater than a threshold percentage, and generating a notification based on whether the percentage of time points is greater than a threshold percentage. 
     
     
       16. The method of  claim 15 , wherein the threshold percentage is about 95%, the DTA value is about 3 mm, and the specified absolute dose difference threshold is about 3% from a planned absolute dose. 
     
     
       17. The method of  claim 14 , wherein determining whether the treatment plan meets specified quality criteria comprises calculating a gamma metric that combines a DTA value of fluence isodoses and an absolute dose difference between the delivered dose map, and generating a notification of whether the calculated gamma metric meets a threshold gamma level. 
     
     
       18. The method of  claim 11 , wherein the partial image x i  comprises positron emission activity data. 
     
     
       19. The method of  claim 18 , wherein the positron emission activity data comprises one or more of PET data, lines-of-responses (LOR) data, and PET detector signals. 
     
     
       20. The method of  claim 19 , wherein the LOR data and/or PET detector signals comprise simulated LOR data and/or PET detector signals. 
     
     
       21. The method of  claim 4 , wherein a signal to noise ratio (SNR) of the partial image x i  of the target region is less than a SNR of the previously-acquired image X of the target region.